1. Field of the Invention
The present invention relates to a heater block for preheating a lead frame in a wire bonder for electrically connecting a semiconductor to the lead frame by bonding opposite ends of a plurality of wires, such as gold wires, and more particularly to a multi heater block of such a wire bonder in which one heater block preheats various kinds of lead frames having different paddle size so that the exchange time and the manufacturing expense of the heater block due to the change of kind of the lead frame are reduced.
2. Description of the Prior Art
Conventionally, wire bonding is performed after preheating a lead frame at a predetermined temperature as a bonding pad of a semiconductor chip is electrically connected to an inner lead of a lead frame by bonding opposite ends of a plurality of wires, such as gold wires, respectively. Accordingly, the wire bonder is generally provided with a heater block for preheating the lead frame transferred thereto.
With reference to FIG. 1A which shows a known heater block body including a paddle seating part 2 protruded thereon at a predetermined heighth, for example 0.5 mm, of which a paddle seating groove 2a is provided inside the paddle seating part 2 for allowing the size of the paddle seating groove 2a to be corresponded to the paddle size of the specific lead frame and paddle support seating grooves 2b and 2c are provided on the front and rear portions of the paddle seating groove 2a so as to be seated a paddle support for allowing the paddle of the lead frame to be connected and supported.
On the other hand, as shown in FIG. 1B, the paddle seating part 2 is not protruded, and the paddle seating groove 2a and the paddle support seating grooves 2b and 2c are formed in the upper surface of the heater block body 1.
As the size of the paddle seating groove 2a shown in FIGS. 1A and 1B is corresponded to the paddle size of the specific lead frame and a heater (not shown) is disposed inside the heater block body 1, the lead frame can be preheated.
The operation for preheating the lead frame by using the heater block according to the prior art as constructed above is as follows:
First, the heater block fit in the paddle seating groove 2a according to the paddle size of the lead frame to be preheated is mounted on the upper surface of the wire bonder body (not shown) and the height for bonding a wire is adjusted by that of the heater block mount.
When a wire bonding is performed after mounting the heater block in the wire bonder as described above, the lead frame to be preheated is transferred to the upper surface of the heater block by means of a lead frame transferring system (not shown) so that the paddle of the lead frame transferred is seated in the paddle seating groove 2a of the heater block. In result, the lead frame is preheated to the proper temperature for performing a wire bonding by means of heater disposed in the heater block body 1.
Namely, the lead frame is transferred on the upper portion of the heater block and then the paddle thereof is seated into the paddle seating groove 2a so that the lead frame may be preheated by heater (not shown) disposed in the heater block body 1 of the lower portion of the paddle seating part 2 for a prescribed time.
Then, when the preheating of the lead frame is completed at the heater block, a bonding pad of the semiconductor chip and an inner lead is bonded through a plurality of gold wires by the wire bonder and then transferred by the transferring system of the lead frame.
On the other hand, when the paddle size of the lead frame is changed, the heater block having the paddle seating groove 2a fit in the changed paddle size is mounted in the wire bonder after disjointing the heater block mounted in the wire bonder so that the wire bonding is performed by preheating the lead frame as described above.
However, the known heater block should be manufactured by different paddle sizes with corresponding paddle seating grooves 2a, thus causing the cost to be increased. Also, since the heater block should be changed every time the size of the paddle varies, much down time occurs.
In other words, the height of the heater block mount should be adjusted every time the heater block is changed due to the change of the working package. Further, after completing the adjustment, the working should be performed only next to the evalution. Therefore, the known heater block has disadvantage in that it badly affect in the productivity due to the relatively longer down time according to the exchange and the adjustment of the equipment.